The sophistication of a present-day electronic system is a result of complex functions handled by integrated circuits making up the electronic system. Within a single silicon chip or wafer, numerous integrated circuits are fabricated. Each integrated circuit may comprise many millions of transistors, including associated diodes, resistors, and capacitors, interconnected to form complex electronic systems capable of performing various functions.
Semiconductor integrated circuits comprise the majority of electronic circuits in computers and other digital electronic products. Integrated circuits can be configured, for example, as a central processing unit (CPU), a programmable logic array (PLA), an application specific integrated circuit (ASIC), or a digital signal processor (DSP). Both the sophistication and speed of operation of these integrated circuits has rapidly increased due to improvements in integrated circuit manufacturing technologies resulting in smaller and faster devices.
Once a computer or another digital electronic product is manufactured, it is important to test various aspects of the system to verify proper operation. For example, the interconnection between two integrated circuits must be verified. In addition, it must be verified that a specific integrated circuit is operating properly. In most circumstances, the communication between two integrated circuits is facilitated by a data bus, which includes first and second communication links. The first and second communication links provide bi-directional communication between the first and second integrated circuits such that communication in a first direction is provided by a first communication link while communication in a second direction is provided by the second communication link.
In order to test or "debug" systems having bi-directional communication links between two integrated circuits, prior art analyzation systems included an analyzing device, such as a logic analyzer or an oscilloscope. The analyzing device includes two leads which are electrically connected to the first and second communication links. During a testing operation of the system, the analyzing device observes the data being communicated between the first and second integrated circuits via the first and second communication links. This information is then compared to information which is expected to be observed between the first and second integrated circuits. If the two sets of information coincide, it is assumed that the communication links and adjacent integrated circuits are properly installed and functioning. Conversely, if the two sets of information do not coincide, it is assumed that a portion of the system is not operating as designed.
Another prior art embodiment for testing and debugging a system includes dedicating numerous pins within an integrated circuit for repeating or copying a communication link, which may be observed without disrupting normal operation of the system. However, this approach is very costly in terms of chip pinout, in that numerous additional pins are dedicated solely for test purposes, rather than operational purposes.
The speed with which computers and electronic devices operate has drastically increased in the recent past. For example, computers are capable of operating at frequencies in the high megahertz to gigahertz range. However, the technology relating to analyzing devices such as logic analyzers or oscilloscopes, has not increased in such magnitude. Rather, most analyzing devices are not capable of operating at frequencies in the mid megahertz to low gigahertz range. Thus, interconnecting an analyzer device directly to communication lines within a present day electronics system will disrupt and disturb the normal operation of the system, perhaps rendering the system inoperable. Therefore, there is a need for a system and method which will permit observation and debugging of bi-directional information transmitted on first and second communication links between first and second integrated circuit such that the overall performance of the system will not be inhibited and that a minimal number of pins are used.